Abstract: A reciprocating engine with a variable compression ratio mechanism is disclosed. A lubrication system of the engine is improved by controlling an oil pressure according to a compression ratio setting. The lubrication system includes various combinations of control valves and oil passages. The oil relief passage is opened at a high compression ratio setting applied to a low engine load range and is otherwise closed at a low compression ratio setting applied to a high engine load range.

Abstract: In a compression ratio controlling apparatus and method for a spark-ignited internal combustion engine, the variable compression ratio mechanism is controlled by a compression controlling section on the basis of a detected engine speed and engine load in such a manner that the compression ratio is varied toward a target high compression ratio when the engine load falls in a predetermined low load region and toward a target low compression ratio when the engine load falls in a predetermined high load region and a predetermined delay is provided in a variation in the compression ratio toward one of the target high and low compression ratios in accordance with at least one of an engine driving history immediately before a transient state of a change in the engine load occurs and a wall temperature of a combustion chamber of the engine immediately before the transient state thereof occurs.

Abstract: A link mechanism of an engine includes: an upper link having a first end connected to a piston pin of a piston; a lower link connected to the upper link via an upper pin having a center, the lower link being connected to a crank pin of a crank shaft; a control shaft extending substantially in parallel with the crank shaft, the control shaft having a rotational center; and a control link including: a first end swingably connected to the control shaft, and a second end connected to the lower link. In a process of the center of the upper pin moving nearer to the axial line of the piston pin, the center of the control pin moves in the upward direction, thus inclining the lower link and allowing the center of the upper pin and the center of the piston pin to move in the downward direction.

Abstract: A control apparatus for an internal combustion engine includes a variable compression ratio mechanism capable of varying a compression ratio of the engine, a compression ratio setting section that sets a compression ratio to be attained by the variable compression ratio mechanism in accordance with an operating condition of the engine, a knock detecting section that detects a knock occurrence state, an ignition timing learning correcting section that determines a learning correction value of an ignition timing in accordance with the knock occurrence sate, and a compression ratio correcting section that corrects the compression ratio set by the compression ratio setting section in accordance with the learning correction value of the ignition timing. A control method is also provided.

Abstract: A combustion control system for a spark-ignition internal combustion engine includes a variable piston stroke characteristic mechanism changing a compression ratio of the engine, sensors detecting engine operating conditions, i.e., engine speed and engine load, and at least one of a variable lift and working angle control mechanism simultaneously continuously changing an intake-valve lift and an intake-valve working angle and a variable phase control mechanism changing an angular phase at a central angle corresponding to a maximum valve lift point of the intake valve. Also provided is a control unit that controls the variable piston stroke characteristic mechanism, and at least one of the variable lift and working angle control mechanism and the variable phase control mechanism, depending on the engine operating conditions.

Abstract: A reciprocating engine with a variable compression ratio mechanism is disclosed. A lubrication system of the engine is improved by controlling an oil pressure according to a compression ratio setting. The lubrication system includes various combinations of control valves and oil passages. The oil relief passage is opened at a high compression ratio setting applied to a low engine load range and is otherwise closed at a low compression ratio setting applied to a high engine load range.

Abstract: An internal combustion engine has a variable compression ratio mechanism operatable during an intake stroke to change an actual compression ratio of the engine, and is capable of correcting an amount of fuel injected into the engine in response to a change in the compression ratio.

Abstract: A link mechanism usable for a variable compression ratio mechanism of an internal combustion engine includes first and second links pivotally connected by a pin inserted through cylindrical first and second pin boss portions of the first and second links. Each of the first and second pin boss portions includes a circumferentially extending first narrow section, and a circumferentially extending first wide section having an axial wall thickness greater than the axial wall thickness of the first narrow section. The wide sections of the first and second pin boss portions are overlapped in an region extending in the axial direction of the pin.

Abstract: A control system for an internal combustion engine is provided. The engine includes a compression ratio control mechanism and an ignition timing control system. The control system comprises an engine control for controlling the compression ratio control mechanism and the ignition timing control system so that when the engine is cold, the ignition timing is retarded largely from an MBT point and the compression ratio is set higher than that obtained when the engine is cold and operated at corresponding engine rpm and engine load. A method for controlling such an internal combustion engine is also provided.

Abstract: In a compression ratio controlling apparatus and method for a spark-ignited internal combustion engine, the variable compression ratio mechanism is controlled by a compression controlling section on the basis of a detected engine speed and engine load in such a manner that the compression ratio is varied toward a target high compression ratio when the engine load falls in a predetermined low load region and toward a target low compression ratio when the engine load falls in a predetermined high load region and a predetermined delay is provided in a variation in the compression ratio toward one of the target high and low compression ratios in accordance with at least one of an engine driving history immediately before a transient state of a change in the engine load occurs and a wall temperature of a combustion chamber of the engine immediately before the transient state thereof occurs.

Abstract: A control system for an internal combustion engine is provided. The engine includes a compression ratio control mechanism and an ignition timing control system. The control system comprises an engine control for controlling the compression ratio control mechanism and the ignition timing control system so that the compression ratio is varied depending upon variations of engine rpm, engine load and a warm-up condition of the engine and that when the engine is cold, the ignition timing is retarded from a MBT point and a top dead center position of a piston is made lower in level than that obtained when the engine is hot and operated at corresponding engine rpm and engine load. A method for controlling such an internal combustion engine is also provided.

Abstract: In a variable compression ratio mechanism for an internal combustion engine employing an upper link, a lower link, and a control link, the lower link includes a crankpin bearing portion into which a crankpin is fitted, a first connecting-pin bearing portion into which a first connecting pin for the upper link is fitted, and a second connecting-pin bearing portion into which a second connecting pin for the control link is fitted. A central connecting portion is provided to connect an axial central portion of at least one of the first and second connecting-pin bearing portions to an axial central portion of the crankpin bearing portion. The central connecting portion has an axial length L1 shorter than each of an axial length L2 of the crankpin bearing portion, an axial length L3 of the first connecting-pin bearing portion, and an axial length L4 of the second connecting-pin bearing portion.

Abstract: A control system for an internal combustion engine is provided. The engine includes a compression ratio control mechanism and an ignition timing control system. The control system comprises an engine control for controlling the compression ratio control mechanism and the ignition timing control system so that the compression ratio is varied depending upon variations of engine rpm, engine load and a warm-up condition of the engine and that when the engine is cold, the ignition timing is retarded from a MBT point and a top dead center position of a piston is made lower in level than that obtained when the engine is hot and operated at corresponding engine rpm and engine load. A method for controlling such an internal combustion engine is also provided.

Abstract: In a rockable-cam equipped reciprocating internal combustion engine, a rockable cam is rotatably fitted on the outer periphery of an intake-valve drive shaft that is rotatable in synchronism with rotation of a crankshaft. The rockable cam oscillates within predetermined limits during rotation of the intake-valve drive shaft so as to directly push an intake-valve lifter. As viewed from an axial direction of the crankshaft, an axis of the intake-valve drive shaft is offset from a centerline of the intake-valve stem in a first direction that is normal to both the cylinder centerline and the crankshaft axis and directed from the cylinder centerline to the intake valve side. The crankshaft axis is also offset from the cylinder centerline in the first direction.

Abstract: A link mechanism of an engine includes: an upper link having a first end connected to a piston pin of a piston; a lower link connected to the upper link via an upper pin having a center, the lower link being connected to a crank pin of a crank shaft; a control shaft extending substantially in parallel with the crank shaft, the control shaft having a rotational center; and a control link including: a first end swingably connected to the control shaft, and a second end connected to the lower link. In a process of the center of the upper pin moving nearer to the axial line of the piston pin, the center of the control pin moves in the upward direction, thus inclining the lower link and allowing the center of the upper pin and the center of the piston pin to move in the downward direction.

Abstract: A piston crank mechanism of an internal combustion engine includes an upper link connected to a piston, a lower link connected to both the upper link and a crankpin, and a control link through which the lower link is linked to an eccentric cam of a control shaft to restrict the degree of freedom of the lower link. By varying the angular position of the eccentric cam with respect to the control-shaft axis, the center of oscillating motion of the control link varies, thus varying a compression ratio. The center of gravity of the lower link, determined by an equivalent inertia weight obtained by adding weights of connecting pins and weights of the upper-link boss-shaped end and the control-link boss-shaped end connected to the lower link via the respective connecting pins to the lower-link self-weight, is situated closer to the center of the crankpin.

Abstract: In an internal combustion engine of variable compression ratio type, a piston control mechanism is employed which comprises a lower link rotatably disposed on a crank pin of a crankshaft of the engine, an upper link having one end pivotally connected to the lower link and the other end pivotally connected to a piston of the engine, a control link having one end pivotally connected to the lower link; and a position changing mechanism which changes a supporting axis about which the other end of the control link turns. When the piston comes up to a top dead center, a compression load is applied to the control link in an axial direction of the control link in accordance with an upward inertial load of the piston.

Abstract: A control system for an internal combustion engine is provided which comprises a compression ratio control mechanism and a control unit for controlling the compression ratio control mechanism. The control unit including an acceleration parameter obtaining section for obtaining an acceleration parameter corresponding to a change of an engine speed, an acceleration determining section for determining whether the engine is in a slow or fast acceleration state on the basis of the acceleration parameter, and a control section for controlling at least one of a compression ratio change speed at which the engine compression ratio during engine acceleration is changed and a compression ratio change start time at which a change of the engine compression ratio during engine acceleration is started, on the basis of whether the engine is in a slow or fast acceleration state. A control method is also provided.

Abstract: A combustion control system for a spark-ignition internal combustion engine includes a variable piston stroke characteristic mechanism changing a compression ratio of the engine, sensors detecting engine operating conditions, i.e., engine speed and engine load, and at least one of a variable lift and working angle control mechanism simultaneously continuously changing an intake-valve lift and an intake-valve working angle and a variable phase control mechanism changing an angular phase at a central angle corresponding to a maximum valve lift point of the intake valve. Also provided is a control unit that controls the variable piston stroke characteristic mechanism, and at least one of the variable lift and working angle control mechanism and the variable phase control mechanism, depending on the engine operating conditions.

Abstract: A variable compression ratio mechanism for a reciprocating engine includes a connecting rod split into upper and lower connecting rod portions linked to each other through a first connecting pin. A rockable arm is oscillatingly linked at one end to the lower connecting rod portion through a second connecting pin. A control mechanism shifts the center of oscillating motion of the rockable arm to vary a compression ratio of the engine. A piston stroke is set to be greater than two times a crank radius of a crank, irrespective of variations in the compression ratio. A linkage is dimensioned and laid out, so that its crankpin load is less than a crankpin load produced by a linkage that the crankpin is located on a perpendicular line at substantially the midpoint of a line segment between and including the centers of the first and second connecting pins.